> But remember that hiring is hard, and managers are loath to fire someone they've already spent so much effort finding, hiring, and onboarding. Finding someone else to do it can take weeks, months, or longer! Which in many cases risks killing the project altogether.

Anecdata. One of my colleague got fired for not meeting expectations at his level for two consecutive halves. From what I've seen, he was competent and provided value to the project. Some companies have high turnover and are functioning with the idea that everyone is replaceable.